1. Field of the Invention
The present invention relates in general to a manufacturing process and system for forming a flexible connection in a hollow metal device and in particular to a method and system that utilizes an abrasive waterjet system and method for a machining the flexible connection in the hollow metal device.
2. Description of the Related Art
Flexible connections that transmit both torque and thrust from a driving element to a driven element are well known in the art. For example, in U.S. Pat. No. 3,260,069, a flexible connection is disclosed for use in the construction of a well drilling apparatus. In such well drilling apparatus, a relatively stationary drill string is employed near the lower end of which there is a fluid operated motor. The motor may be of the type having an outer stator and an inner rotor. The well drilling apparatus, on having circulation fluid discharged downwardly therethrough and through the drill string, functions as a fluid-operated motor and is operatively connected to a rotary well drilling bit that is rotatably mounted at the extreme lower end of the drill string. The rotary well drilling bit rotates about an axis which is stationary in relation to the drill string but the lower end or the rotor of the fluid-operated motor moves in a gyratory path in relation to the drill string. Consequently, a flexible connection must be provided between the gyrating lower end of the motor and the well drilling bit, which rotates about a stationary axis, that will transmit torque from the rotor to the well drilling bit to forcibly rotate the well drilling bit. It is well known that such a connection must not only be flexible and capable of transmitting torque but also should be capable of transmitting thrust so that the rotor will not be expelled by the circulatory fluid from its stator. This, of course, is only one illustration of the type of flexible connection with which the present invention is concerned and it is not to be restricted thereto. On the contrary, it may be employed in any situation where it is desirable or necessary to be able to transmit flexible torques of great magnitude and thrusts of great magnitude.
The flexible connection disclosed in U.S. Pat. No. 3,260,069 is formed in a tubular member that is transversely divided into a plurality of segments having mutually interfitting portions that enable torque to be transmitted from each segment to its neighbor. These segments are formed by cutting a heavy walled tube with a cutting torch on tortuous paths such that each segment is, in effect, provided with lobes that loosely fit between corresponding lobes on the adjacent segment. Each lobe is widest near its extremity than elsewhere so that although there is a clearance space between each lobe and the adjacent segment, the segments of the tubular member are, in effect, locked against total separation from each other. Generally, an oxy-acetylene torch is used to cut the tortuous path in the hollow tube. The procedure produces a rough cut finished surface with the inside diameter of the surface typically having burnout points at the bottom of the flexible coupling lobe profile. The burn-out points create stress risers during operation. As a result, the end of the flexible coupling lobe has a tendency to crack and/or break off. In addition, considerable handwork is required because of slag cleanup after the oxy-acetylene torch cutting and because of the rough surface finish of the flexible coupling lobe faces. Further, the rough surface finish of the flexible coupling lobe faces causes premature wear.
A plasma torch cutting procedure improves the flexible coupling lobe surface finish. Even though minimal burn-out points are experienced with this procedure, those remaining burn-out points still create stress risers during operation. Further, even with the plasma torch cutting procedure, there is still considerable handwork related to slag cleanup and premature wear occurs due to the rough surface finish of the flexible coupling lobe faces.
Also, when utilizing the known procedures of oxy-acetylene and plasma torch cutting, the flexible coupling lobe profile must be heat treated after cutting. However, these cutting methods produce an inconsistency in material properties that result in a poor quality heat treatment and carburization within the area of the lobe cut profile.
Further, the previous procedures of oxy-acetylene and plasma torch cutting cause poor consistency of quality in relation to the accuracy of the part. In addition, smaller diameter parts are more difficult to control with respect to good surface finish and a minimum occurrence of burn-out points at the bottom of the flexible coupling lobe profile.
Finally, kerf width requirements are difficult to achieve with the previous procedures of oxy-acetylene and plasma torch cutting.